Outlook Add-in targeting 2007 & 2010

I have an Outlook Add-in that I have developed for Outlook 2007. I am working on having this add-in work on Outlook 2010 as well. My add-in is an adjoining region on the appointment/meeting request window that displays a WPF control. The add-in installs fine on Outlook 2010 but when I go to the a开发者_运维问答ppointment/meeting request window I have a blank adjoining region. Any thoughts on what is preventing my WPF control from showing in Outlook 2010?

Thanks